Duplication and partitioning in evolution and function of homoeologous Q loci governing domestication characters in polyploid wheat

• Published in: Proceedings of the National Academy of Sciences - PNAS 2011-11, Vol.108 (46), p.18737-18742
• Main Authors: Zhang, Zengcui, Belcram, Harry, Gornicki, Piotr, Charles, Mathieu, Just, Jeremy, Huneau, Cecile, Magdelenat, Ghislaine, Couloux, Arnaud, Samain, Sylvie, Gill, Bikram S, Rasmussen, Jack B, Barbe, Valerie, Faris, Justin D, Chalhoub, Boulos
• Format: Article
• Language: English
• Subjects: 3' Untranslated Regions; Alleles; Biological Sciences; Chromosomes; Chromosomes - genetics; conserved sequences; domestication; evolution; Evolution, Molecular; Exons; Gene Duplication; Gene loci; Genes; Genetic loci; Genome, Plant; Genomes; Genotype & phenotype; Hexaploidy; intergenic DNA; Introns; Life Sciences; loci; Models, Genetic; Mutation; Mya; nucleotide sequences; Phenotype; Phenotypic traits; Plant domestication; Ploidies; Polyploidy; Pseudogenes; RNA, Messenger - metabolism; transcription factors; Triticum - genetics; Triticum aestivum; Vegetal Biology; Wheat
• ISSN: 1091-6490; 0027-8424; 1091-6490
• DOI: 10.1073/pnas.1110552108

The Q gene encodes an AP2-like transcription factor that played an important role in domestication of polyploid wheat. The chromosome 5A Q alleles (5AQ and 5Aq) have been well studied, but much less is known about the q alleles on wheat homoeologous chromosomes 5B (5Bq) and 5D (5Dq). We investigated the organization, evolution, and function of the Q/q homoeoalleles in hexaploid wheat (Triticum aestivum L.). Q/q gene sequences are highly conserved within and among the A, B, and D genomes of hexaploid wheat, the A and B genomes of tetraploid wheat, and the A, S, and D genomes of the diploid progenitors, but the intergenic regions of the Q/q locus are highly divergent among homoeologous genomes. Duplication of the q gene 5.8 Mya was likely followed by selective loss of one of the copies from the A genome progenitor and the other copy from the B, D, and S genomes. A recent V329-to-I mutation in the A lineage is correlated with the Q phenotype. The 5Bq homoeoalleles became a pseudogene after allotetraploidization. Expression analysis indicated that the homoeoalleles are coregulated in a complex manner. Combined phenotypic and expression analysis indicated that, whereas 5AQ plays a major role in conferring domestication-related traits, 5Dq contributes directly and 5Bq indirectly to suppression of the speltoid phenotype. The evolution of the Q/q loci in polyploid wheat resulted in the hyperfunctionalization of 5AQ, pseudogenization of 5Bq, and subfunctionalization of 5Dq, all contributing to the domestication traits.